Kraken currently does this... they have most major currencies. I used to use CAD to price cryptos since that's what I earn... but it became difficult to think that way when things were going up and down very fast. Bitcoin brought some stability to the situation. But you do bring up a great point regarding bitcoin weighing down other cryptos. I'm not sure if trading in dollars will completely correct this as large stocks do the same thing on the NYSE... it's due to the competition for liquidity. When bitcoin starts to fall traders will see it as a buying opportunity and sell other coins to raise the cash. If it drops 50%+ like it currently is doing, a lot of traders start to think it's a great time to get back in.